'Sensory Tricks' in Dystonia Examined

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Note that this study was published as an abstract and presented at a conference. These data and conclusions should be considered to be preliminary until published in a peer-reviewed journal.

The mystery of how "sensory tricks" adopted by patients to relieve symptoms of dystonia work is beginning to be unraveled.

Point out that results of the studies suggest that dystonia is not just a motor-function disorder but involves other neuronal processes.

PHILADELPHIA -- The mystery of how "sensory tricks" adopted by patients to relieve symptoms of dystonia work is beginning to be unraveled, research presented here suggested.

Analysis of videos of 138 participants in the Dystonia Coalition research project confirmed that such tricks -- such as applying a light touch to the affected part of the body, also called an alleviating maneuver or geste antagoniste -- were partially effective in 43% and completely effective in 40%, reported Neepa Patel, MD, who conducted the research at Baylor College of Medicine in Houston and is now at the University of Texas Southwestern Medical Center in Dallas.

That such tricks really work suggests that dystonia is not just a motor-function disorder but involves other neuronal processes, Patel and colleagues suggested.

Such dysfunction was also reflected in a measure of neuronal excitability performed with transcranial magnetic stimulation (TMS), in a separate study by Ubaldo Del Carro, MD, of Ospedale San Raffaele Scientific Institute in Milan, and colleagues.

As summarized by Vesper Ramos, MD, and colleagues at the National Institutes of Health (NIH) in Bethesda, Md., a wide range of tricks has been reported helpful in various types of dystonia.

For cervical dystonia, several reports documented effectiveness of raising an arm and placing a finger near the dystonic muscles, either not touching the face or before touching it. Another reported maneuver has been for the patient to forcibly counteract the involuntary contraction by pushing the chin or forehead in the opposite direction.

Some patients with blepharospasm have devised attachments to their eyeglasses that touch the eyelid when it spasms, the NIH researchers found.

And writers' cramp has reportedly been relieved with various tricks, such as switching to a larger or smaller pen, as well as touching the dystonic hand with a finger on the other hand.

Patel told MedPage Today that patients develop these tricks on their own through trial and error. As far as her group could tell, no single approach appears to work better than others.

Her study collected demographic and clinical data on Dystonia Coalition project participants, who have been recruited to provide systematic observational data on the features and natural histories of these conditions.

For the current analysis, Patel and colleagues examined the data for 154 individuals with cervical dystonia, of whom 138 reported using sensory tricks to relieve the involuntary movements.

Trick users and nonusers were both 60 years old on average. Users tended to have had a longer dystonia duration and more severe symptoms as measured with the Global Dystonia Rating Scale and the Toronto Western Spasmodic Torticollis Rating Scale.

But after adjusting for age, dystonia duration, and presence of psychiatric conditions, the associations between trick use and global or cervical symptom severity did not approach significance.

Analysis of their tricks indicated that most preferred an ipsilateral light touch on the lower face (59 patients), chin (48), or posterior neck (29). Smatterings of the others used forceful ipsilateral touch, light or forceful contralateral touch, or bilateral maneuvers.

These findings don't just document a simple way to relieve symptoms -- they may also shed light on the underlying pathology of dystonia.

In particular, Patel and colleagues argued in their poster, the utility of sensory tricks "supports emerging theories that dystonia is a disorder of sensorimotor integration."

The Italian researchers explored another aspect of dystonia biology in their study, the role of motor cortex excitability, using TMS. Although this technology is now best known for its antidepressant effect, it can also trigger motor responses when focused on the relevant areas of the brain.

Del Carro and colleagues enrolled eight cervical dystonia patients who were being treated with botulinum toxin and who used sensory tricks to further relieve symptoms, along with eight healthy controls. The researchers used paired-pulse TMS aimed at the motor cortex areas controlling patients' hands -- first while the participant's head was turned in a dystonic-like fashion, and then while the patient's hand gently pushed the head back into the normal position.

Motor-evoked potentials in the hand not used to perform the trick provided measurements of intracortical inhibition and facilitation.

Facilitation was significantly increased in the dystonia patients relative to controls while their heads were turned, the researchers found. But when the patients performed their sensory tricks, their facilitation was lower than in the head-turned condition and equivalent to that seen in controls. Intracortical inhibition, on the other hand, did not differ between controls and patients during either experimental condition.

Del Carro and colleagues said these findings represent the first evidence of a physiological basis for sensory tricks involving motor cortex excitability -- in particular, that the sensory trick "produces its effect by inhibiting the overactivity of the motor cortex."

Study authors declared they had no relevant financial interests.

Reviewed by Robert Jasmer, MD Associate Clinical Professor of Medicine, University of California, San Francisco

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